Fusible link and strut



May 18, 1926. 1,584,719

1.. A. BISSON FUSIBLE LINK AND STRUT Filed August 5, 1920 E1 2227' ,JTEZ' Ea Q 9 3 g INVENTGI? Fatented May 18, 1926 u m: STATE P cs.

LOUIS A. BIssoN, or PHILADELPHIA, PENNSYLVANIA, AssIGNon, BY MESNE AssIGN- MENTS, T GENERAL FIRE EXTINGTJISHER COMPANY, or PROVIDENCE, RHODE IsLANn, A CORPORATION or DELAWARE.

FUSIBLE LINK AND STRUT.

My invention relates to fusible links or struts of the type used in connection, with thermally affected devices such as,-for eX- ample, sprinkler heads in fire extinguishing systems and apparatus, safety devices on fire doors, actuating devices for fire alarms, refrigerating apparatus and similar means.

Among the objects of my invention is to 7 provide a new and useful fusible link or strut in which the thermally affected element, preferably a fusible substance, will be normally under compression when in static and unfused condition.

Another object of my invention is to provide a new and useful means of the character aforesaid which will be free from the shearing and tearing stresses .pr sent in the prior devices thus wholly avoiding the cold-flow action that is incidental to the 29 subjection of the fusible substance to such stresses, and, hence prevent premature operation of the controlled means.

A further object of my invention is to so construct the links and struts made in ac- 5 cordance with my invention that the elements thereof will be mutually thrown apart or asunder without danger ofthe same clogging or rendering the controlledmeans inoperative or merely partly operative.

A. still further object is to provide the link or strut, so constructed, with heat insulating means whereby the link and strut will be of utility on sprinkler systems employing steam, hot water or other mediums normally at a temperature which if imposed upon the thermally active element, such as the fusible substance, would cause its operation.

A still furtherobject is to construct the link or strut whereby the presence of the active element, such as the fusible substance, will be visible and also so exposing the same that it can be readily and easily tested.

A still further object is to provide the link or strut with means whereby an as sured operation may be effected at the desired instant.

Other objects are to so construct and proportion the parts that "great strength may be obtained in a relatively small and light weight means, that the required elasticity may be secured to give the structure an instantaneous and snappy action when set into operation; and to arrange the parts relative to each other whereby the restraining capacity thereof will be at a maximum, the forces, normally stressing the same, being directed along lines of greatest effort for a rapid operation, but not with any tendency to produce any premature operation.

Other objects and advantages of my invention will more fully appear hereinafter.

Referring to the accompanying drawing where the same or similar reference characters are used to designate corresponding parts in the various views,

Fig. 1 is a view in elevation of a sprinkler head, embodying one form of device constructed in accordance with the invention;

Fig. 2 is a view in transverse section of one form of strain member constructed in accordance with the invention;

Figs. 3, a and 5 are similar views of other forms of strain members; 7

Fig. 6 is a View in elevation of a strain member showing additional fusible material in the gap between the elements of the strain member;

Fig. 7 is a view in elevation of a link embodying the invention;

Figs. 8, 9 and 10 are views in elevation illustrating lever types of struts embodying the invention;

Fig. 11 is a view in elevation illustrating a toggle type of strut embodying the invention; r

Fig. 12 is a view in elevation illustrating a thrust type of st ut embodying the invention; 7

Figs. 13 and 14 are views partly in section and elevation illustrating means for heat insulating the strain member utilized many of the foregoing structures.

Referring more particularly to the drawing upon which are illustrated several representative modes of utilizing my invention, 1 have shown, as in Fig. 1, a sprinkler head comprising a nipple 1 provided with suitable means, as screw threads, for securement thereof to a conduit of a fire extinguishing sprinkler system or the like. The nipple is provided with yoke arms 2 extending upwardly to aspray head 3 of any suitable type located opposite and in spaced relation to an outlet nozzle fl, the latter being normally closed by a closure cap 5. The spray head 3 may be provided with a threaded stem 6 adapted to be adjustably rotated in a nut 7 preferably formed integral with the yoke arms 2. Any means, such as a pin 8, may be utilized to permanently maintain the stem 6 in adjusted position. Both the stem 6 and the cap 5 may be provided with pivotal projections 9 and 10 respectively axially aligned and coincident with the axis of the nipple 1 and spray head 3.

Between said projections 9 and 10 may be located a strain member or fusible strut comprising aligned retaining or socl'et elements 11 and 12 appropriately rece. ed an end of each to suitably and conveniently receive the pivotal projections 9 and 10 respectively. If, however, it be desired to form the ends of the strain member parts 11 and 12 with projections in lieu of recesses, the projections 9 and 10, in that event should become recesses to receive the projections of said strain member- The other end of each of said socket elements is cut or tapered an acute angle to provide surfaces 13 and 14.- respectively, on the elements 11 and 12, and the elements are so located with relation to each other that those faces will normally lie sub stantially parallel to each other and in spaced relation, or out of contact with each other, thereby providing an oblique gap 15 therebetween.

The tapered ends of said retaining or socket elements are further provided with recesses 16 and 17 adapted to receive the ends of a bar, rod strip or block of thermally sensitive or fusible material 18 having the property of fusing, melting, crumbling or otherwise disintegrating at a. definite and predetermined temperature, but remainl- S. L:

ing normally rigid under other degrees of temperature or conditions. The member or material 18 is of such length as to seat at its ends against the bottoms 19 and 26 of the recesses 16 and 17 and to extend through and be visible in the gap 15. It will be further observed that member 18 is of a size to fill the recesses 16 and 17 so that the walls of the latter act as supports therefor against any possible lateral tendency to movement of the material of the member 18. It is further noted that the gap 15 is made relatively narrow or thin so that while the surfaces 13 and 14 are normally out of contact, the space through which the member 18 extends, in said gap, without lateral support, is so small that strain or cold-flow action of the material of the member 18 cannot occur and consequently the member 18 will not become shortened under a continued application of pressure or force.

The surfaces 13 and 14 are inclined or formed oblique in order that when the member 18 ceases, by reason of fusing or melting, to maintain the retaining or socket elements 11 and 12 in normally spaced relation the member 12 may be caused to move, due to the pressure of the fluid in the nozzle l acting against the cap 5, toward the element 11 whereupon the inclined face 1% contacts with the face 13 and slides thereover whereby the elements are laterally cast from the sprinkler head. This act is substantially instantaneous and is completed before the extinguishing fluid issues from the nozzle l.

lVhile I have shown a strain member in Fig. 1 in position for receiving the full thrust or pressure of the extinguishing fluid it is noted that the invention coinprehends the utility of means constructed in accordance with the invention for operating under forces that are merely component forces of or derived from the pressure of the extinguishing fluid in the sprinkler system. F-xamples thereof are shown in Figs. 8, 9, 16 and 11.

Referring to Fig. 8, a lever type of strut is shown comprising an L-shaped lever member 21 provided with a recess 22 adapted to receive the projection 10 on the cap 5, and arms 23 and 2%, the former extending upwardly and the latter laterally. The upper end of the arm 23 is provided with a fulcrum point or ridge 25 upon which is fulcrumed a lever 26, intermediate its ends, with one end thereof provided with a recess 27 adapted to receive the projection 9 on the stem 6, the other end of the lever 26 extending toward the free end 28 of the arm 21. The end 28 is appropriately shaped, as in the form of a hook, to present an end 29 opposite the end 30 of the lever 26. Between these ends, 29 and 80, may be interposed one of the strain members forming part of my invention, the recesses at the ends thereof respectively receiving the ends 30 and 29. It ill be observed that the lever 26 is of such a length that when the strain element is properly assembled in place relative thereto and the member 28, the lever 26 and the strain member form an obtuse angle slightly less than 18 O with the lever 26 normally urging to increase said angle to 180. \Vhencver the temperature of the surrounding atmosphere, and consequently the fusible member, reaches that at which the latter fuses or melts, the strain member will immediately collapse due to the toggling effect of the lever 26 moving the socket element 11 toward the socket element 12, whereupon the inclined faces thereof contact and slide over each other, and the lever consequently released. The parts are cast aside and the s; riukler head permitted to open as above disclosed in connection with Fig. 1. It will be noted here that the. strain member is normally placed under a very small component force of that acting at the nozzle and consequently the tendency for cold-flow of the fus ble material 18 is accordingly reduced. The lever 26, as well as the arm 2%, has a certain the. strain members.

amount of resiliency so that as soon as the strain member starts to collapse the rendering asunder of the link or strut structure will be very sudden or with snap.

The strut structure shown in Fig. 10 is similar to that shown in Fig. 8 and comprises a strut or lever'member 21 provided with a'recess 22 adapted to receive projection 10 and an arm 23, a laterally extending hook portion 28 being integrally provided near the lower end of the member 21. A lever 26 is fulcrumed upon the upper end of the arm 23 and is provided with a recess 27 adapted to receive the projection 9 on the stem 6, the other end 30 being in engagement in an end recess of the strain member interposed therebetween and the end 29 of the projection 28- As in'the structure shown in Fig. 8, the lever 26 and the strain member are at an obtuse angle less than 180 and as soon as the fusible material 18 fuses or melts the lever 26, being normally under urging force to move away from the arm 23, causes the strain member to collapse and force itself therefrom whereby the strut structure is cast asunder.

The strut structures illustrated in Figs. 9 and 11 are more in the nature of toggle struts, the former partaking, to a certain extent, characteristics of the forms of devices shown in Figs. 8 and 10 and the latter being more of the nature of a simple toggle. The strut shown in Fig. 9 comprises a pair of mutually engageable levers 21 and 26*, the former being somewhat longer than the latter, and provided at its free end with a preferably integral hook portion 28*. Each member 21" and 26 may be provided with toggle legs or sections .31 and 32 respectively, the latter having an end 33 fulcrumed in a recessed: end34 of the former, the lower end '35 of the member 31 and the upper end 36 of the member 32 respectively adapted to be fulcrumed in recesses 9 and 10 suitably provided in the stem 6 and cap 5, such recesses 9 and 10 being provided in lieu of the projections 9' and 10, as in the form of device shown in Fig. 1. The free end of the lever 26 may be provided with an end 30 slightly Lip-turned, as shown, in spaced rela tion and opposite to an end 29 where the same are received in the end recesses, of

The latter is so interposed therebetween as to form with the upturned portion of the lever 26 an obtuse angle slightly less than 180, as in the forms shown in Figs. 8 and 10, hereinbefore des ribed. As soon as the fusible material 18, fuses, melts or crumbles, the lever 26 being normally under urging force to move away from the arm of lever 21 causes the strain memberto collapse and free itself therefrom whereby the strut structure is cast asunder, as in the forms above described and shown of the device shown in Fig. 9. Each of the lever members 31 and 32 is provided with a laterally extending .arm 21 and 26 posed in substantially parallel and spaced relation to receive and normally maintain therebetween the strain member forming a part of the herein disclosed invention. This strain member may extend throughout the length of the space provided between the members 21 and 26 with the socket elements 11 and 12 thereof abutting the same, but if desired, and preferably so, blocks 37 and 38 of any suitable rigid material, preferably heat insulating substance, maybe interposed between the respective socket members 11 and 12 and the arms '21 and 26 which tend to approach each other. The pressure between the contacting parts, particularly the elements, 11, 12, 37, 38, 21 and 26 will be normally sufiicient to maintain the same in position until the proper conditions existto cause a correct operation of the device, but it may be noted that if it be desired, the members 21 26 11 and 12 may be provided with recesses 39, 40, 17 and 16 respectively adapted to receive counterpart projections 39, 40, 29? and 30 formed on the ends of the blocks 37 and 38. In this fashion the strain member and the blocks 37 and 38 will be assured against lateral movement and consequent disengagement from each other or from the members 21 or 26", asfrom vibrations or other causes, whereby premature operation may be avoided. When the fusible material 18, however, melts or otherwise yields the parts 11 and 12 will approach and slide over each other, to be cast aside and consequently the arms 21 and 26 will also rapidily approach each other to a point where the toggle structure will be. cast asunder, similarly to the action of the other forms of device described in the foregoing.

In Fig. 7 is shown a tension strut or link embodying the invention- It comprises a .pa1r of side members 41 and 42 each provided at an end thereof with laterally extending thrust pieces 43 and 44 respectively and at the other ends thereof with suitably apertured bent portions 45 and 46 by which the parts 41 and 42 may be attached to tensioning elements adapted to pass through the apertures 47 a-nd 48 thereof. The members 41 and 42' are so assembled as to present the abutment pieces or portions in opposed spaced relation and a strain member may be interposed therebetween with the opposite ends or such strain member abutting said thrust members 13 and 11. The portions to and alt are laterally bent or otlset from the body portions of the members 41 and 42 in order to locate them in alignment and coincident with the axis or the longitudinal medial plane of the strain member whereby the line of force or tension acting through the link organization will be along a central line or plane. it the line of force tending to render the link structure asunder were at an angle to said line or plane, there would be a greater tendency for the members e21 and to rock the strain member whereby the members ll and l2 might separate and operate pren'iaturel x. Where the line 0t thrust parallel to sail members 11 and -12 and along the axis or longitudinal medial plane of the strain member, such action can not occur. in use, the thrust pieces 4-3 and $1 normally tend to approach each other, and therefore, when the material 18 yields, as by melting or crmnbling, the socket members 1.1 and 12 will approach and slide over each other so as to cause the members 41 and -12 to more laterally away from each other. This move ment will be ample for the elements -13 and d-al to clear each other as they more toward each other.

In Fig. 12 is shown a strut or thrust link comprising a pair of thrust plates -19 and 50 adapted to slide longitudinally along each other. They may be placed in contact with each other. as shown, and at a slight angle to the line of thrust or force acting on the cap 5, whereby the upper and lower ends and 52, respectively, of the plates a9 and 50, may be received in suitable recesses, as recesses 9' and 10 formed in the stem and cap 5 respectively. Near the ends 51 and 52 may be formed on the plates 19 and 50 laterally disposed retaining sockets and 5 1, corresponding to the retaining or socket member 11 of 1, and the other ends of the plates 51 and 52, respectively are formed with terminal retaining sockets 55 and 56, corresponding to the retaining or socket member 12 of Fig. 1. These sockets, in pairs, namely 53 aligned with 56 and 5 1 aligned with form strain members for the strut or thrust link structure, there being two strain members instead of one. Two strain members, however, are not essential inasmuch one would sutiie. The aligned socket members and 5" 5i and 55 are, as in the terms shown Figs. 1 and appropriate y recessed to conveniently receive a bar, rod, strip or block of thermally sensitive or fusible 111?- teria] 18 having" the property of fusing, melting, crumbling or otherwise disintegrating at a definite and predetermined temperatur but remaining; normally rigid under other degrees of temperature and conditions. Each of the sockets 53, 5d, 55 and 56 is out or tap -Ml at acute angle to provide surfaces which normally will lie substantiaii parallel to each other with the faces of the sockets and 56 or and 51- in slight spaced relation to provide therebetween an oblique gap, as the gap 15 in the form shown in Figs. 1 and 2. Normally, the plates l9 and 50 are under a strain and tend to move or slide along each other but are restrained from such movement by reason of the bars or blocks of material 18 maintaining said plates in position with the tapered ends of the sockets thereof in spaced relation. As soon, l1ov-.'cver. as the material 18 yields, the plates 49 and 50 in:- mediately slide relatively to each other until the inclined surfaces of the adjaccnil located and aligned sockets come into contact. Further mo l'enient will cause the sockets or socket portions on said plates to slide over each other and to cause the plates 1!) and to laterall separate and be cast asunder, in the case oi. the parts 11 and iiying apart in Fig. 1.

in of the strain members herein desruaed or referred to may, if desired, be provided with means for more ei'i'ectivcl causing the operation the device, particularly when a relativel hard and slow acting thermally sensible or fusible material is being used. fuch means is illustrated in Fig. 3, wherein the retaining or socket members 11 and 12 may be provided with cutting edges 57 and 58 so that as the faces 13 and 1e slide over each other the cutting edges 57 and 58 will readily cut the material 18 thereby aiding and hastening the action of strain member. For the purpose of forming said cutting edges without the same forming or occupyingany groove or recess in the bar or block of material 18 and without removing a substantially large amount of material from the inner walls of the sockets, small back cuts or recesses 59 and 60 maybe made in the walls of the socket members 11 and 12, adjacent the faces 13 and 14;, so as to provide the sharp edges 57 and It will be noted .lso that these cutting edges are located ;o as 0 cut the material on opposite sides ind substantially along the same surface or plane. the surfaces and 1% being, at the. time of action oi the cutting edges. in contact with each other, and consequently in the same plane.

The strain member or element may be of n desired form and cross-section. and as n illustration of a desi able form, I have shown in Fig. 4: one of double conoidal sl ape, coth the socket members 11 and 1'3 d the thermally sensitive material 18 be ng tapered at the ends, the points or ends 61 and 62 of the socket members 11 and 12" being adapted to be received in the re= cesses 9 and 10 of the stem 6 and cap 0. This form of stram member is strongest when following the lines of a parabola so- 7 of force acting therethrou-gh. The socket members, also may be made thin, light and devold of corners or pro ections whereby the pro ection of the same by the sprinkler head parts may be facilitated and effected with a minimum chance for interference as the elements or parts of the strut or link structure are cast asunder. It may also be observed that the corners 57 and 58 may also serve as shearing or cutting edges when the 1nember18' is in a state of fusing and as the inclined surfaces of the members 11 and .12 slide over each other.

In some cases it may be desirable to make the retaining elements of the strain member of thin metal. In that event the inclined surfaces, 13 and 1a would not have sufficient area of contact to insure efficient operation of the parts. I have shown in Fig.

. 5, in part, a strain member with the retaining elements or sockets made of thin metal. Each socket member 11 and 12 may be pro vided with laterally extending fins 63 and 6 1 on'the adjacent inclined ends thereof, with faces or surfaces 13 and 1 1 of sufficient area to give proper sliding contact therebetween. These fins maybe of any shape or form desired to accomplish the end sought, those shown in Fig. 5 being in theform of flanges preferably spun into the form shown for the socket members 11- and 12.

Where sprinkler heads are to be used in a system using hot water or steam as. an extinguishing medium or agent it is obvious that the heat would ordinarily be conducted by the metal of the sprinkler head to the fusible link or strut, which is also of metal,

and would cause the operation of the same at an undesirable time. In order that the de vice constructed in accordance with my 1nvention may be of use in sprinkler heads in systems using hot water or steam, which is at a temperature higher than that at which the material 18 or 18' fuses, I may provide heat insulating means therefor. In Figs. 13 and 14 I have shown two modes of insulating the strain member from the other parts of the link or strutstructure. In Fig. 13

the ends of the strain member may be pro-. vided with caps 65 made of any suitable heat inuslating material, such as hard rubber, bakelite, paper fibre, or similar materials. The cap may be provided with two recesses 66 and 67, the former to receive an end of the strain member and the other to receive heat insulating materials 68, such as asbestos or compositionscomprising asbestos as an essential ingredient and similar materials. Within the recess 67 may project and press against the material 68 the ends 9 or 10 of the stem 6- and cap 5, or the ends 29 and 30 of the hook'28 and the lever 26, or the ends 29 and 30 of the hook 28 and lever 26, or the ends 29 and 30 of the hook 28 and the lever 26, or the projections 29 and 30 of the blocks 37 and 38, or the ends 61 and 62 of the strain member shown in Fig. 4.

Fig. 14 is somewhat similar to Fig. 13, except that the ends of the strain member are recessed to receive hollow bodies 69, such as glass spheres, having a vacuum therein. These evacuated bodies will act as efficient insulators of heat. Inasmuch as glass itself is a poor conductor of heat, it will be apparent that the heat that the glass may itself conduct will be inappreciable. The other parts of the strut or link structure with which the strainmember is tobe associated It is preferable, however, to omit such material in said gap. One of the reasons for this is that an inspection of the strain element may be made by looking through the gap to perceive the presence of the bar, pieceor block of fusible material 18 in place. With the material 70 in place in the gap 15 there is no assurance that the bar or block 18 is in place since it is possible to omit it and merely fill the material 7 O in said gap, which, of course, would permit cold-flow action and consequently the operation of the strain member prematurely. By having the gap '15 always open it is possible to visually ascertain the presence of the element 18.

The gap 15 also offers a space for the introduction of a test element, such as a needle, which may be moved through the gap 15 with the point of the needle against the element 18. If the element 18 is of the proper.

14, by the point of the needle. The invention is therefore both adapted to visibility and test of the yieldable element.

While I have herein described and illustrated upon the drawing some embodiments of my invention it is to be understood that the invention is not limited to the particular details and arrangement of parts shown and described, but that the invention comprehends other forms, details and arrangements of parts as do not depart from the spirit of the herein-disclosed inventionand the scope of the appended claims.

Having thus described my invention what I claim and desire to secure by United States Letters Patent is 1. In a sprinkler head, the combination of normally spaced members and thermally yieldable means for normally maintaining said members in spaced relation, said mem bers being movable toward each other upon the yielding of said means, and means for normally maintaining said yieldable means substantially free from strain.

2. In a sprinkler head, the combination of normally spaced members, said members being provided with opposed inclined surfaces, thermally yieldable means between said members normally maintaining said members in spaced relation, said members being movable toward and slidable over each other upon the yielding of said means, and means for normally supporting said yieldable means against cold flow.

3. A strut for fire extinguishers comprising a thermally yieldable member and means for normally placing said member under compression, said means being adapted upon the yielding of said member to be cast asunder and being adapted also for normally sustaining said yieldable member from strain.

4. A strut for fire extinguishers, comprising a thermally yieldable member, and means for normally placing said yieldable member under compression, said means comprising spaced members adapted upon the yielding of said yieldable member to engage each other for the casting asunder thereof, and means for supporting said yieldable member against cold flow when normally placed under compression.

5. A strut for fire extinguishers, comprising a thermally yieldable member, and means for normally placing said yieldable member under compression, said means comprising spaced members having opposed inclined surfaces adapted to engage with and slide over each other upon the yielding of said yieldable member for the casting asunder of said members, and means for laterally supporting said yieldable member against cold flow when normally placed un der compression.

6. A strut for fire extinguishers, comprising a thermally yieldable member and recessed members on said yieldable member, the ends of said yieldable member being seated in the recesses of said recessed members, said recessed members being normally maintained in spaced relation by said yieldable member and adapted upon the yielding of said yieldable member to engage each other for the casting asunder thereof.

7. A strain element for thermally controlled devices, comprising aligned recessed retaining members and thermally yieldable means seated in the recesses of said retaining members whereby the latter are normally maintained in spaced relation and adapted to engage each other upon the yielding of said yieldable means.

8. A. strain element for thermally controlled devices, comprising aligned reces ed retaining members and thermally yieldable means placed under compression between said retaining members, said yieldable means being seated in the recesses of said retaining members whereby the latter are normally n'iaintained in spaced relation, said retaining members being provided with opposed inclined surfaces adapted upon the yielding of said yieldable means to mutually contact and cause said retaining members to slide over each other along said inclined surfaces.

9. A strainelement for thermally controlled devices, comprising aligned recessed retaining members, thermally yieldable means extending in the recesses of said retaining member and placed under compression therebetween, said yieldable means normally maintaining said retaining members in spaced relation, said retaining members being provided with opposed inclined surfaces adapted upon the yielding of said yieldable means to mutually contact and cause said retaining members to slide over each other along said inclined surfaces and means on said retaining members for laterally supporting said yieldable means.

10. A strain element for thermally controlled devices, comprising aligned recessed retaining members, thermally yieldable means extending in the recesses of said retaining member and placed under compression therebet-ween, said yieldable means normally maintaining said retaining members in spaced relation, said retaining members being provided with opposed inclined surfaces adapted upon the yielding of said yieldable means to mutually contact and cause said retaining members to slide over each other along said inclined surfaces and means on said retaining members for shearing said yieldable means curing the relative movement of said retaining members.

11. A strain element for thermally controlled devices, comprising aligned recessed retaining members, thermally yieldable means extending in the recesses of said retaining member and placed under compres sion therebteween, said yeildable means normally maintaining said retaining members in spaced relation, said retaining members being provided with opposed inclined surfaces adapted upon the yielding of said yieldable means to mutually contact and cause said retaining members to slide over each other along said inclined surfaces and cutting edges adjacent said inclined sur faces for cutting said yieldable means during the relative movement of said retaining members.

12. A strain element for thermally con trolled devices, comprising spaced retaining members, thermally yieldable means placed under compression between said retaining members for normally maintaining the same in spaced relation, said retaining membersbeing provided with inclined surfaces located in spaced parallel relation, and means for afi'ording a lateralsupport for saidthermally yieldable means when placed under compression, said retaining members adapted upon the yielding of said yieldable means to mutually contact and relatively slide along said inclined surfaces for a casting asunder thereof.

13. A strain element for thermally controlled devices, comprising spaced compression members, thermally yieldable means placed under compression between said com pression members, and operative to normally maintain said compression members in spaced relation, means on said compression members operative upon the yielding of said yieldable means to cast said members asunder as said members move toward each other and heat insulating means on said compression members.

14. In a sprinkler head, the combination of a strut, a lever fulcrumed on said strut, a strain element having thermally yieldable means placed under compression and being interposed between said strut and said lever substantially without receiving direct stress therefrom transversely of'the line of compression and normally restraining the separation of said strut and lever.

15. In a sprinkler head, the combination of mutually fulcrumed levers, a strain memher having a thermally yieldable means placed under compression between said levers, substantially without receiving direct stress therefrom transversely of the line of compression whereby upon yielding of said strain membersaid levers are cast asunder.

16. In a sprinkler head, the combination of mutually fulerumed levers, a strain member having a thermally yieldable means placed under compression by said levers, sub

stantially without receiving direct stress therefrom transversely of the line of compresslon, said member normally maintaining said levers in inoperative position, one

of said levers and said strain member forming an angle less than a straight angle, said strain member and said last mentioned lever being urged to form a straight angle upon the yielding of said strain member.

17. In a sprinkler, the combination of a strut, a lever fulcrumed on said strut, fus ible material placed under compression interposed between said strut and said lever and normally restraining the separation of said strut and lever.

18. In a sprinkler head, the combination of a pair of spaced members, said members being provided with inclined surfaces adjacently located in spaced parallel relation, fusible material interposed between said members and normally maintaining said members and said surfaces in spaced relation, said member having means for laterally supporting said fusible material when normally placed under a stress, and means for placing said fusible material under strain whereby, when the fusible material yields upon a rise in temperature, said members move toward and slide over each other for a casting asunder thereof.

19. A link or strut for thermally controlled devices, comprising relatively movable members and thermally yieldable strain material placed under compression by said members, substantially without receiving direct stress therefrom transversely of the line of compression, said strain means normally maintaining said members in0perative, said members being operative to mutually separate upon the yielding of said strain means.

20. A link or strut for thermally controlled devices, comprising relatively movable in mbers and thermally yieldable strain material normally placed under compression by said members, substantially without receiving direct stress therefrom transversely of the line of compression, said strain means being provided with opposed inclined surfaces normally out of contact with each other, said members operative upon yielding of said strain means to mutually separate by the sliding contact of said inclined surfaces.

21. A strain element for thermally controlled devices, comprising relatively movable members, fusible material placed under compression by said members, said fusible material normally maintaining said members in spaced relation, means on said members operative upon the fusing of said fusible material to cause a mutual separation of said members, and heat insulating means on said members adapted to insulate said members and said fusible material from the conduction of heat thereto.

22. In a sprinkler head, the combination of relatively movable members, a thermally yieldable strain member comprising fusible material placed under compression by said movable members, said strain member normally maintaining said movable members in inoperative position, means 011 said strain member operative upon fusing of said fusible material to cause a yielding oi said strain member and heat insulating materlal be- LOUIS A. BISSON. 

